It looks like it might be an easy night for Newt Gingrich in South Carolina.

What at one time looked like a blowout Romney win, and then a nail biter, appears to be shaping up to be a laugher for Gingrich.

Nate Silver:

Much of the reason for the relatively clear lead for Mr. Gingrich is that he has very clear momentum in the race. In a survey conducted by Public Policy Polling, for instance, Mr. Gingrich led Mr. Romney by 4 percentage points in interviews conducted on Wednesday night, based on a detailed breakout of nightly results provided to FiveThirtyEight by Tom Jensen of Public Policy Polling. But Mr. Gingrich's lead expanded to 6 points in interviews conducted on Thursday. And Mr. Gingrich led by 14 points in about 700 interviews conducted on Friday night, after the Thursday night debate in North Charleston and the interview given to ABC News by one of Mr. Gingrich's ex-wives.

In primaries, especially in the early-voting states, momentum is a strong predictor of the results, and it is usually correct to give considerable weight to the most recent data.

South Carolina has been surveyed by more than a dozen distinct polling firms over the past week, and the surveys are in agreement that Mr. Gingrich gained significant ground on Mr. Romney after the Monday night debate in Myrtle Beach. If Mr. Gingrich was also helped by the Thursday night debate, as the Public Policy Polling data suggests, his margin of victory in South Carolina could be impressive - perhaps reaching into the double digits.

Nevertheless, Mr. Romney retains some chance of winning. Although momentum holds up more often than not in primaries and caucuses, there have been some important exceptions - like when Hillary Rodham Clinton won the New Hampshire primary in 2008 despite Barack Obama's polling surge following his Iowa caucus win.

If there is a backlash against Gingrich as a result of the remarks about open marriage by his ex-wife, it isn't showing up in the latest polls. But it's hard to factor in something so recent, nor is it easy to peer into the voting booth as the large number of undecideds - 21% in that PPP poll - contemplate their choices.

Gingrich may have won the debate, the primary, - and perhaps the nomination - with his salvo at the media during the first few minutes of Thursday night's debate. That's what the right wants from their candidate and Newt gave it to them in very dramatic fashion.

We might look back on that moment the same way we recall Ronald Reagan's outburst in a New Hampshire gym prior to another debate in 1980. "I'm paying for this microphone, Mr. Breen" elicited the same kind of response from GOP voters nationwide that Gingrich's "No - but I will" is getting today.

The worm turns again in South Carolina.